The invention relates to a method for charging an auxiliary voltage source found on a boat with an electric drive, which auxiliary voltage source provides power for at least one additional component, wherein a main voltage source, which provides power for the electric drive, is found on the boat.
The invention concerns a boat with electric drive with associated DC voltage source for power supply to various electric components, in particular drive components, and with a further DC voltage source for supplying power to control and monitoring components, for example.
It is often necessary to provide two separate energy stores, for example batteries, in a boat with electric drive. The necessity of using two energy stores can result, for example, from different requirements in terms of availability for the drive/power components and the control components. Components of the power circuit and components of the control circuit often have different requirements for the level of the supply voltage, with the result that energy stores with different voltages must be provided.
For this reason, a main voltage source for supplying power to the power components, for example the electric drive, in particular the electric motor, and an auxiliary voltage source for supplying power to the control components, for example, are provided on the boat. Since the power components have the higher power requirement, the energy content of the main voltage source is greater than the energy content of the auxiliary voltage source.
The problem addressed by the present invention is to propose a device and a method for charging the auxiliary voltage source of a boat.
This problem is addressed by the embodiments disclosed herein.
The boat is connected to a voltage source on land in order to charge the main voltage source. The invention enables the auxiliary voltage source to be charged from the main voltage source. The auxiliary voltage source therefore does not need to be connected to a power supply on land. Therefore, only one interface/connection point between the electrical installation on board the boat and the land needs to be produced.
In order to use the boat, the boat must be disconnected from the land connection, with the result that the charging of the main voltage source is discontinued. Once the land connection has been disconnected, it is possible according to embodiments of the invention also to charge the auxiliary voltage source from the main voltage source. Thus, a sufficient state of charge of the auxiliary voltage source and hence a reliable supply to the control components and, in particular, safety components can also be ensured during the trip.
In general on a boat, all of the safety-related components, for instance an emergency stop loop, an insulation monitor, a water monitor, a drive controller or a GPS, are connected to the auxiliary voltage source. At the same time, the additional components used for comfort, for instance cooling units, heating elements, lighting, are usually connected to the auxiliary voltage source. There exists the danger that the auxiliary voltage source is loaded so heavily and discharged so much by said additional electrical consumers that the energy content of said auxiliary voltage source decreases to a value which is no longer sufficient to supply the safety components with power.
The safety components are used, for example, to switch the connection terminals of a high-voltage source to be isolated from the supply in the event of problems. Thus, for example, in the event of a failure of a safety component, the electrical connection between the cells of the main voltage source and the connection terminals of the main voltage source can be interrupted, with the result that the electric drive connected to the connection terminals is no longer supplied with power, although the main voltage source still has a sufficient energy content. The boat becomes no longer maneuverable, as a result of which a situation which is dangerous for the crew of the boat can arise. According to embodiments of the invention, the possibility then exists to charge the auxiliary voltage source on board the boat from the main voltage source.
In a boat with a high-power electric drive, the electric drive is often designed as a high-voltage system in order to maintain the power level in the drive system in a controllable manner. The control, monitoring and safety devices with which the electric drive is controlled, monitored and made safe are not power components, however, and are therefore often designed as low-voltage systems. In an embodiment of the invention, therefore, a high-voltage source is provided as main voltage source and a low-voltage source is provided as auxiliary voltage source.
In particular, voltage sources with a terminal voltage of more than 60 volts, more than 100 volts or more than 200 volts should be referred to as high-voltage sources. A low-voltage source should preferably have a terminal voltage of at most 48 volts, at most 24 volts or at most 12 volts.
According to embodiments of the invention, the auxiliary voltage source, in particular a low-voltage source, is charged from the main voltage source, in particular a high-voltage source. For this purpose, an auxiliary charging device for the auxiliary voltage source is provided, which auxiliary charging device is connected to the main voltage source and which charges the auxiliary voltage source from the main voltage source. Thus, for example, in the case of a main voltage source designed as a high-voltage source and an auxiliary voltage source designed as a low-voltage source, the auxiliary charging device is provided with a DC-to-DC converter by means of which the higher voltage of the high-voltage source can be transformed into the lower voltage level of the auxiliary voltage source.
The main voltage source is used for supplying power to the electric drive, in particular to an electric motor. The electric drive has a significantly higher power than the auxiliary units which are connected to the auxiliary voltage source. Correspondingly, the main voltage source has a significantly higher energy content than the auxiliary voltage source. The main charging device for charging the main voltage source correspondingly likewise has a significantly higher power than a charging device for charging the auxiliary voltage source. Preferably, the main charging device is configured such that it can simultaneously charge the main voltage source and the auxiliary voltage source connected to the main voltage source in a predefined time period. Since, for this purpose, the main charging device only needs to apply slightly more power in comparison to charging the main voltage source alone, the main charging device can be designed with a low extra capacity such that it can additionally supply the auxiliary voltage source.
Both the main voltage source and the auxiliary voltage source are preferably designed as rechargeable batteries. The embodiments described herein can be used in the case of batteries with any desired cell chemistry. Preferably, lithium batteries, lithium-ion batteries, lithium-manganese batteries or lithium-manganese-cobalt batteries are used as voltage sources, as main and/or auxiliary voltage source.
High-voltage sources often have their own control device. Said control device is often supplied by a low-voltage source. For the user's safety, for example, a control device can be provided which ensures that the high-voltage source can switch its voltage at its connection terminals only if said control device is supplied by a low-voltage source. That is to say that the low-voltage source must already be available before the start of the charging of the high-voltage source.
Preferably, a low-voltage source is provided which has an energy content that is sufficiently large that it still enables the connection of the high-voltage source after a usual time period in the event of a discharge, which is to be taken into account, by additional components and further consumers and in the case of assumed self-discharge. Preferably, the low-voltage source has a charge of at least 30 Ah, preferably at least 40 Ah. In the case of a sport boat, a battery suitable for this would have, for example, at least 44 Ah.
After the high-voltage source is connected, the low-voltage source can be charged from the high-voltage source. At the same time, however, the high-voltage source can also be charged by means of a main charging device. The main charging device for the high-voltage source should therefore have a power which is suitable for simultaneously charging the high-voltage and low-voltage sources.
The main voltage source can be charged by a main charging device which is found on the boat or on land. If the main charging device is found on land, a DC voltage connection between the land and the boat is necessary. If the charging device for the main voltage source is found on the boat, an AC voltage connection between the land and the boat is necessary.
Since the auxiliary voltage source can also be used to supply additional components, an electrical decoupling of the power supply of the additional components and the power supply of the system and safety-related components is advantageous.
This is achieved, for example, by the power supply of the additional components and the power supply of the safety-related components being decoupled from one another by means of a switch or a reverse-blocking valve, for instance by means of a diode, with the result that a drop in the power supply of the additional components does not disrupt the power supply of the safety-related components.
The auxiliary voltage source is preferably used as power supply for the additional components and the safety-related components are advantageously supplied with power via a DC-to-DC converter from the main voltage source. The power supply via the auxiliary voltage source ensures that the additional components are reliably supplied even in the event of a pulse-shaped power demand. The operation of an auxiliary motor for trimming and/or tilting of an outboard motor is a typical pulse load which must be buffered by the auxiliary voltage source.
If a temporary overloading of the auxiliary voltage source were to occur, the operation of the safety-related components would not be impaired since said components have their own power supply and are decoupled from the auxiliary voltage source by a switch or a reverse-blocking valve.
In particular, a diode can be used as reverse-blocking valve. In order to reduce the forward losses, the diode can be replaced by an inversely driven MOSFET, the channel of which is additionally switched on when current flows via the inverse diode.
Provided the main voltage source is not yet connected, in particular when the voltage is not yet present across the connection terminals of the main voltage source, the safety-related components cannot be supplied via the DC-to-DC converter from the main voltage source, either. In this case, the power supply of the safety-related components takes place via the reverse-blocking valve which allows current to flow only in the direction from the auxiliary voltage source to the safety-related components and not vice versa. That means that, before the main voltage source is switched on, the safety-related components are supplied from the auxiliary voltage source via a switch or a reverse-blocking valve. Since the main voltage source is often safeguarded by a safety-related component, for example a protection and control circuit, and can only be switched on when the respective safety-related component enables the switch-on, it is ensured that the main voltage source can be switched on and, after the switch-on, the power supply of the safety-related components takes place via the DC-to-DC converter.
The method according to embodiments of the invention for charging the auxiliary voltage source allows the charging of main voltage source and the auxiliary voltage source at different times. The auxiliary voltage source can be charged independently of the charging of the main voltage source. In particular, the auxiliary voltage source can also be charged when the boat has not berthed on land.
The invention and further details of the invention are explained in more detail in the following exemplary embodiments.